Rigidity

Ok... I really need a high speed spindle machine that is bigger, faster and
has better wear characteristics than the Taig. The Hurco is coming along
nicely, but it definitely does not have a high speed spindle. Not even
close. I've played with the idea of just using a router on it like I did
the Taig, but then its kind of a headache to deal with switching spindles in
control. No horrible, but not great. I have not found a speed multiplier I
can afford so I was thinking about making my own belt drive spindle with
pulley's to multiply speed, and then just mount it with a router-esque style
spindle mount on the quill of the Hurco. Yeah, it's a lot of work, but with
some planning I would not have to do any controler changes when going from
one spindle to the other. Just load a different machine profile depending
on which spindle I planned to use. This leaves coolant spray. At 25K-35K
RPM even a 1/32" cuter throws coolant everywhere. I put the Taig in a full
enclosure because of it, and it works pretty good. Putting the Hurco in a
full enclosure is problematic at best. If I stick with 5000 RPM and slower
machining with the stock spindle (not suited for my most common jobs) I
could use a fence on the table, like Iggy and other have used on their knee
mills, but it won't even come close to containing the spray of a high speed
spindle. Maybe some form of accordion way covers that slide on rails inside
the the top of the fence pushed back and forth by the quill?
Alternatively, I could just use the Hurco to make gantry style router
machines. Well some of the parts. My concern then is (as the title of this
post says) is rigidity. Most gantry router machines are made out of
aluminum. Since I actually push a cutter hard enough to momentarily bog a
1HP router from time to time would they be rigid enough for the job? I
really don't have or plan to have the facilities to melt and pour cast iron
so my thoughts were could I get somewhere in between by making the gantry
routers out of C-channel steel. The Hurco could certainly do all the
cutting on it. My big concern is that I recall discussions here and
elsewhere about harmonics, etc in regards to why machine tools are machined
cast iron rather than steel.
No I can't really afford the step up to a "real" high speed machine yet.

Reply to
Bob La Londe
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Are you sure of this statement?
i
I put the Taig in a full
Reply to
Ignoramus10693
When you get up to that speed, you probably would be better off running dry. High-speed milling is generally done dry these days, or with a very lean mist of vegatable oil. VW uses peanut oil.
At those speeds, in commercial milling of steel or iron, cutters typically are multi-coated. If the top coat or the second coat is aluminum oxide, as it often is for cutters made for high-speed machining, using coolant will wreck your cutters in a hurry.
Reply to
Ed Huntress
Well, my router(s) turns upto 35K (actually a little faster no load - checked with an optical tach) and coolant hits all four walls of the enclosure. Well three. The front is a clear plastic shower curtain until I get around to making a plexiglass door. It hits the sides solidly upto about a foot above the table at over a foot away from the cutter in all directions. Not a solid stream, but some spray hits every surface of the enclosure including the roof. You might argue that the air from the router fan is part of the problem, but the net result is the same. Most of my cutting is with larger than 1/32", but it throws coolant around too.
Or were you arguing that what I am using isn't really coolant? LOL. Or the semantics of the word "everywhere" since you probably haven't felt any spray from my machine(s). ROFL.

Reply to
Bob La Londe
I can get about (depending on the size) 20-30 hours out of an uncoated solid carbide cutter with "coolant/lubricant". How that compares to other stuff I don't know. Any form of dry cutting will dull the cutter and result in chip weld and machine crash in a fraction of that time. With the coolant/lubricant the cut quality just gets progressively worse with more ragged edges to knock off as the cutter gets older.
I have some 3/32" Al-Tain coated cutters from Reid that give me 15-18 hours of near perfect cutting with flood. They will continue to cut passabley for another 8-10 hours after that. Without flood I had constant problems with them and almost threw them away. I am using that at near full flute plunge, but a step of only a few thousandths.
I've gotten a lot of useful information out of this group, but I've also found that sometimes things work for me inspite of "common knowledge."
******************************************************* So nobody has an opinion about coolant containment? Or rigidity of a machine made out of steel vs aluminum vs potential harmonic ringing vs cast iron?
*
****** Those were what I actually asked. *******
This high speed stuff is for 3D machining aluminum with cutters running from 3/32" to 1/4" mostly and occasionally down to 1/32" or rarely upto 1/2". I do try to plan the jobs so the smaller cutters (1mm etc) are only used to cut those features which require them.
Feed slow some will say and just use a slower spindle. In answer I say. Feeding slower is the answer, but not the answer you thought. Feed slower and cut deeper for much faster material removal. Still needs a pretty fast spindle. With a slower spindle you need to feed slow AND cut shallow.
I am routinely running jobs that take 10 hours with no cutter change. I don't have too many jobs in the 20+ hour range since I went to flood coolant/lubricant and I can slow feed in one pass for many jobs now, but there are some.
All that being said I did some decent stuff dry cutting, but it took forever. Some of you guys gave me grief about it too. Told me I wasn't cutting aluminum. Just annoying it.
Anyway, I am doing jobs now in 8-9 hours that took me 20-30 when cutting dry. I'm getting better results, and crashing a lot less often as well. Usually never once I get a good estimate of the cutter life for the job.

Reply to
Bob La Londe
You're getting into an area where you're the only expert.
I use a spindle speeder for my high speed work. Works real good. I think you'd be real happy with one. I also use my pressure mister, a copy of the Henchforth fogbuster. This gives 90% of the cooling of flood with 10% of the mess. I've got a plexiglass hinged sheet that I just stand up to deflect *most* of the coolant.
But it sounds like you do more high speed work in a week than I've done my whole life.
karl
Reply to
Karl Townsend
Well, I have _opinions_ about it, but I'm not an expert. (and I didn't catch this thread until now, so I don't know what you suggested.
I enjoy flood. I use mist sometimes, but don't like it for the mess. Mist (even with a 'fogless' mist applicator) fills the shop and my lungs with coolant fog, and I don't really want to clean it up or breathe it.
I built a four-sided lexan shield system for my mill with movable gates for extreme knee positions. It captures almost every drop. A few fly out the top, but very little, really. It's erected with slot-to-bolt fixturing and a couple of speed nuts. It only takes about 45 seconds to remove or erect.
LLoyd
LLoyd
Reply to
Lloyd E. Sponenburgh
Maybe. I don't know. I've made about 100 molds so far give or take. Some with as many as 22 cavities. A couple of them now live in Australia. A hand full of others are scattered across the states. I've also destroyed more than a couple. LOL.
I've looked for spindle speeders, but the Hurco has a Kwik 200 spindle, and I have a fair amount of tooling for it. End mill holders, a jacobs chuck (good one), and even an Accura-flex collet holder. What I have not found is a speed multiplier for it. I have not looked into the possibility of changing it to some other type of spindle taper. I have seen some adaptors, but haven't followed up too far along that line due to additional cost and compounded runout. For that I can just use a wood router like I am now. Either using a router mounted on the quill or making my own secondary spindle with a pulley for speed multiplying seem to be the options if I want to use that machine for that type of work. If I'm very careful with my planning I can probably do it on the crappy HF mini lathe, but I'm sure I could do it with a better lathe.
The idea of an accordion way cover resting on rails over a table top enclosure pushed back and forth by the quill as the table moves does kind of intrigue me. In fact that idea only really came to me as I typed it earlier. I could picture it in my mind instantly. Not sure what its life would be, but...
Alternatively... while it would take longer I could use the Hurco itself to help increase production by using it to make gantry machines. I have an idea for one that I think would be a perfect fit for most of my work, but I don't know how much the flex of an aluminum frame machine (easy to make or buy most components in 80/20 pieces) will affect my results. Like I said I really want to improve quality over the Taig I'm currently using for that. That's why I was asking if making one out of steel C-channel would be a decent compromise between aluminum and cast iron or if it would be more headache because of its ability to "ring". I certainly don't want to go to the trouble of making machines that I have to run SLOWER.

Reply to
Bob La Londe
What kind of spindle speed are you dealing with? I've seen lots of simple 4 walls bolted together shields for mills, but most of them top out at 5K or less. My 1HP router clocks at upto 35K. Its slowest speed is 8K (roughly).

Reply to
Bob La Londe
If you're cutting aluminum, I must have missed that. It's a different story, and single-layer AlTiN has a completely different set of characteristics from multi-coated tools with an AlOx top coat. The AlOx is for cutting steel and it requires really high cutting temperatures to perform as it's designed. It's actually a vapor-lubricant for cutting steel.
With any of the Al - Ti -N combinations, single-coat or top-coat, cutting aluminum, the big issue is built-up edges. Some of those coatings have an unfortunate habit of the aluminum compound in the coating developing an affinity for the aluminum in the workpiece. Coolant/lubricant will help prevent that -- if you can figure out how to keep it in the cut at 30,000 rpm.
Reply to
Ed Huntress
I wasn't meaning to tweak your nose. Just trying to get some feedback in the specific areas I am working on.
Being able to do high speed spindle work on the Hurco. Hence coolant containment.
Maybe making affordable machines that are better than the Taig. Hence steel vs aluminum with cast not really being a practical option.
I can very easily full contain gantry style machines with a work envelope large enough for what I am doing mostly. The one the Taig is in would contain a gantry machine with a couple times more work envelope.

Reply to
Bob La Londe
Oh, I didn't take it that way, either. You need some accurate information and I was taking you off on a tangent. I wasn't meaning to do that, either. I was just getting too breezy about reading, and I have high-speed milling of steel on my mind again, doing some other research. My experience and research about milling aluminum is mostly at two ends: HSS or plain carbide, and diamond compacts and coatings. I forget that a lot is done with coated carbides (be wary of micrograin carbides with aluminum; the higher cobalt level can cause big problems with built-up edges).
Yeah. Well, we can talk about that; I have some ancient scrolls in my memory from when I was doing articles about machine tool design. First, stay away from wrought iron.
You can use aluminum with proper design for stiffness, but, as you're aware, its coefficient of thermal expansion is around 3X that of steel. That makes it difficult to make anything stable.
As for ringing, yeah, that, too, but the thermal issues tend to be a bigger deal. You may recall that B&S once made a small, cheapish CMM with an aluminum chassis -- early '80s, IIRC. It turned out to be a really bad idea.
Steel weldments are used for very large machines, and even for medium-size machines in Italy and Germany. Stress relief of the welds is their big issue (vibratory stress relief is the usual solution). There have been a number of steel-chassis machines sold in the US over the years, but the idea never stuck. Again, sympathetic vibration can be tricky. But there have been a lot of successful *big* machines built of steel.
The Italians have made some successful machines by building a steel framework and packing it with concrete to take compression loads and to damp vibrations. If you built a steel machine and it vibrates, don't give up. You probably can damp it by applying some viscoelastic goop in strategic places. That's been done with commercially built machines, too.
Well, I can't help with coolant at high spindle speeds.
Reply to
Ed Huntress
Hmmmm.... you got me thinking now. I wasn't planning on welding at all. All precision cut and screwed or bolted together with angle braces for squaring and increased rigidity. With your comments about deadening with concrete that gives me some ideas. All bolting and screwing on flat surfaces (after machining flat and square) lightly tack some mesh inside C-channel. Fill with concrete and bolt together. Not necessarily in that order. It would add substantial weight too for stability. Might need to make some heavier benches though. LOL.
Reply to
Bob La Londe
I've thought about that very thing for a lot of years. Then I got interested in ferrocement and went off in that direction. I still doodle and noodle about it.
But the approach you're talking about is more practical and more certain. Be aware that there are a couple of non-intuitive issues in designing a machine tool. One is that sharp transitions in section tend to "decouple" vibration. You may, for example, have the issues well taken care of for the base, thinking that some concrete there is going to damp vibrations transmitted down from the bed, but you wind up with the vibrations just reflecting back into the bed because it's decoupled by a sharp transition in section. This has actually shown up in years past in conventional lathe construction, where spindle vibration is decoupled from the base (even in cast iron) by a fairly thin section of the head mounting on a big flat pad on the base.
Overall, you probably would learn a lot of useful and interesting things by giving it a try. You have the right idea about using spot-welded mesh or something similar to get a mechancial bond. Concrete doesn't stick well to flat steel when it's vibrated a lot.
Reply to
Ed Huntress
"Bob La Londe" fired this volley in news:rxTeq.6005$ snipped-for-privacy@newsfe14.iad:
I've got a speeder-upper, too -- up to 12K. At that speed, it turns flood into a kind of coarse mist, but it still doesn't get out into the room like the fog from my 'true' mist coolant system.
LLoyd
Reply to
Lloyd E. Sponenburgh
There's a thread with nearly 3000 posts on CNCzone concerning building machines with steel weldements and using epoxy resin and rocks to fill and provide damping. Several machines have been built this way.
Karl
Reply to
Karl Townsend
That sounds like a lot of reading, but it might save Bob more time than he would lose by experimenting with structures that take a while to build.
BTW, those concrete-filled machine tools typically use a polymer-modified concrete that provides better bonding and more vibration resistance than Sakrete.
Reply to
Ed Huntress
I scanned the thread one night. Lot of discussion on the fill material. It was called polymer concrete at some points and epoxy resin at others. Lots of discussion on the proper aggregate and size distribution of it. The whole idea is to dampen vibration.
Karl
Reply to
Karl Townsend
FWIW, there was a lot of money spent in the late '70s and early '80s on developing "concrete" machine tools, some of which were quite successful but most of which cost more in materials and labor than a common cast iron machine tool. It still has some life in it and it continues to hold a lot of promise, particularly for custom machines. I think it was IMTS '82 or maybe '84 that a half-dozen or so showed up on display.
They first tried polymer-modified Portland cement; then polyester resin (not good for the job); and then epoxy with graded granite aggregate. Epoxy/granite was the trick. It's also cost close to $100/gallon for the epoxy. Some builders called the latter "polymer concrete."
But just using the "concrete" as a filler for a steel structure is a different animal and a lot easier to do. Modified Portland cement, something like the materials they use for concrete building repairs, and common graded stone aggregate seems to work OK for that, at a pretty cheap price.
The design issues are a little tricky because the concrete cannot be loaded in tension or in shear at all. It first appears that a small amount of steel can be used to take up tension loads, but that coupling issue is not a trivial thing, so it takes some knowledge of machine structural design to get it right. But it's doable.
Reply to
Ed Huntress
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Does is have a quill? If so, you can clamp a higher-speed spindle, maybe something like a Rockwell/Precise to the side of the quill. This restricts the quill travel some, but may still work. if it doesn't have a quill, but uses a knee or similar vertical movement, then clamp the spindle of your choice to the main head. This gives you a big spindle for heavy jobs like face milling, and the high-speed spindle for the finer work.
Jon
Reply to
Jon Elson

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